Alternating pressure pads are well known for the prevention and management of decubitus ulcers in bedridden patients. The formation of decubitus ulcers, commonly known as bedsores, results from, amongst other things, the pressure applied to certain portions of the skin of a bedridden patient.
Alternating pressure pads generally comprise two sets of alternately inflatable cells; the duration of the inflation and deflation cycles may last from under two minutes for a gentle massaging effect to over twenty minutes.
A high air pressure in the pads may be needed to support the bony protuberances of a patient and to ensure that the patient is lifted sufficiently away from deflated cells of the pad so that adequate pressure relief is provided. A low air pressure, however, is desirable since it provides a pad that is softer and more comfortable. Optimal pressure support therefore not only varies from patient to patient but also during a given inflation cycle of the pad since the pressure supporting points will change during a cycle. The required optimal support pressure will vary even more as a patient changes from a supine to a sitting position.
It is known to provide an automatic pressure controller comprising a sensor pad that is compressible in dependence upon a patient's weight distribution on the alternating pressure pad. If the patient is not suitably supported, the sensor pad will reduce the escape of fluid to exhaust thereby ensuring that more fluid is supplied to the alternating pressure pad until that patient is supported as required.
The fluid flows from the fluid supply line through the pressure pad and from the pressure pad through the sensor pad to exhaust or directly from the sensor pad to exhaust.
This arrangement necessitates the use of multiple connecting tubes between the pump and the mattress. This method is purely pneumatic without any electrical or electronic content added to the mattress, and the pump has to operate continuously at full output for effective performance. The system has to be set up individually when installed. Also, where the sensor pad is within the fluid circuit supplying the pressure pad, the sensor performance is dependent both on the fluid circuit and overall system pressure drops. Moreover, the static performance of the pressure pad is not as effective as the alternating performance as the optimum static pressure cannot be set. It is also known to have a sensor pad within the air circuit as described above but where the fluid is returned back to the pump. The system is prone to the same problems as outlined above.